Increasingly, network applications must communicate with counterparts across disparate networking environments characterized by significantly different sets of physical and operational constraints; wide variations in transmission latency are particularly troublesome. The proposed Interplanetary Internet which must encompass both terrestrial and interplanetary links is an extreme case. An architecture based on a “least common denominator” protocol that can operate successfully and (where required) reliably in multiple disparate environments would simplify the development and deployment of such applications. The Internet protocols are ill suited for this purpose .The three fundamental principles that would underlie a delay-tolerant networking (DTN) architecture and the main structural elements of that architecture, centered on a new end-to-end over lay network protocol called bundling are examined here. The Internet infrastructure adaptations that might yield comparable performance are also examined but it is seen that the simplicity of the DTN architecture promises easier deployment and extension.